Various cable transportation systems, such as chair lifts, gondola lifts, etc. are used to transport skiers from the bottom to the top of a ski run. Such lift apparatus typically comprises spaced tower structures having sheave train assemblies mounted thereon with multiple sheave units for engaging a movable endless haul cable which is driven by suitable drive means at the top and/or bottom of the ski lift. Some sheave units supportively engage the bottom of the cable and other sheave units may depressively engage the top of the cable. Passenger carrying devices such as chairs, gondolas and the like are suitably connected to the haul cable for movement between the bottom and top of the ski run. Such cable transportation systems are often operated in extreme low temperature weather conditions.
In general, the prior art sheave train assemblies comprise a plurality of rotatable sheave members which are rotatably mounted on associated support shaft members by bearing devices with associated lubrication apparatus. Typical sheave train assemblies may comprise 4, 6 or 8 sheave members. Pairs of the sheave members and sheave support shaft members are mounted on opposite ends of sheave support rocker arm apparatus pivotally movable about a central pivot axis. Pairs of the sheave support rocker arm apparatus are pivotally mounted on opposite ends of intermediate pivotal rocker arms which, in turn, may be mounted on a central main pivotal rocker arm. Each rocker arm is pivotally supported by central axle apparatus including grease-type lubrication apparatus. The central axle apparatus comprises a hub member rotatably mounted on a shaft member by axially spaced sleeve-type metallic bearing members with an annular grease chamber therebetween. In order to lubricate the axle assemblies, maintenance personnel must climb the lift towers which is a difficult, laborious procedure. In use, the rocker arm members ordinarily are subject to only very limited pivotal movement of no more than about 10.degree. to 20.degree.. Thus, the lubrication may not be uniformly applied to the entire circumference of the parts subject to relative rotation. Other problems with current apparatus are vibrations and noise created by relative movement between various parts and lack of cushioning between such parts.
A primary object of the present invention is to provide sheave train assembly which requires minimum lubrication with increased durability and decreased wear.
Another object of the invention is to also provide cushioning and vibration dampening means.
Another object of the invention is to reduce cost of construction and maintenance and repair.
In general, the objects of the present invention have been achieved by use of an elastomeric bushing means to couple relatively movable parts without use of lubricant. Each elastomeric bushing means comprise an elastomeric sleeve member mounted in compression in an annular chamber between an outer metallic sleeve member and an inner metallic sleeve member in a manner which enables limited relative arcuate torsional movement therebetween while also absorbing vibration and shock loads and reducing operational noise.